Gutta percha removal

# Best method to remove gutta-percha in retreatment procedures:
A. Hand instrumentation
B. Automated instrumentation
C. Rotatory instruments
D. Ultrasonic instruments

The correct answer is A. Hand instrumentation

The coronal portion of gutta-percha obturations should always be drilled out, preferably by means of endodontic drills such as the Gates-Glidden or Peeso. Gutta-percha may be dissolved (solvent technique) or removed in its solid form (Solid gutta-percha techniques). Dissolving avoids the use of excessive force in the negotiating of gutta-percha-obturated canals.

Extrusion of solvent into the periapical tissues should be prevented.

Solvents of gutta-percha: Gutta-percha is soluble in chloroform, ethyl chloroform, carbon disulfide, carbon tetrachloride, benzene, xylene, eucalyptol oil, halothane, and rectified white turpentine.

Retreatment of solid objects other than gutta-percha, either a silver point or a fragment of an instrument or post, cannot be easily grasped and pulled out. A readily accessible solid object may be withdrawn from the canal by a variety of instruments, including Stieglitz or Perry pliers, a modified Castroviejos needle holder, or a Caulfield silver point extractor. Ultrasonic Vibration, bypassing with hand instruments and Intermittent irrigation, alternating sodium hypochlorite with hydrogen peroxide or RC-Prep, may float the object coronally through the effervescence they create.

Special grasping devices. The Masserann technique- Masserann and alternative extractors. The Masserann kit consists of an extractor into which the object to be retrieved is locked. An assortment of end-cutting trepan burs are used in anticlockwise rotation, to provide access for the extractor. 

Endodontic retreatment

# Endodontic retreatment:
A. Is as technically challenging as original treatment
B. Has a poorer prognosis than original treatment
C. Is performed only on endodontic failures
D. Has different objectives than primary treatment

The correct answer is B. has a poorer prognosis than the original treatment

Post and Core in Endodontics

# In restoring an endodontically treated tooth for post core, an absolute minimum of apical fill of gutta percha to be left over to prevent leakage is:
A. 1 mm
B. 2 mm
C. 3 mm
D. 4 mm

The correct answer is D. 4mm

Since there is greater leakage when only 2-3 mm of Gutta-percha is present, 4-5 mm should be retained apically to ensure an adequate seal. Although studies indicate that 4 mm produce an adequate seal, stopping precisely at 4 mm is difficult, and radiographic angulation errors could lead to retention of less than 4 mm. Therefore, 5 mm of gutta-percha should be retained apically. 

Concentration of EDTA used during BMP:

# Concentration of EDTA used during biomechanical preparation (BMP) is:
A. 20% at pH 7.4
B. 15% at pH 5.0
C. 15% at pH 7.3
D. 25% at pH 7.4

The correct answer is C. 15% at pH 7.3

EDTA has a property of chelate formation with calcium salts. Disodium salt of EDTA is used in endodontic therapy for dissolving pulp stones.